[M4IF Technotes] Using fixed_vop_rate

[Ralph Neff]

Hi,
I have a question on the use of fixed_vop_rate in MPEG-4 
visual.  With fixed_vop_rate == 1, what happens to the
rest of the time fields (e.g. modulo_time_base and 
vop_time_increment)?  Specifically:
  1. If I author a stream and set fixed_vop_rate == 1, do I still
      have to maintain the fields normally used for variable
      display times?  Or can I set them to zero-or-random
      values?
  2. When decoding a file with fixed_vop_rate == 1, should a
      decoder ignore these other time fields?  Or can it use them,
      expecting them to match the fixed rate?
I'm curious because the usual time fields are present in the
syntax even when using fixed_vop_rate mode, so it's not clear
to me whether fixed_vop_rate is intended as a hint or as a
complete override.  Thanks for any help understanding this.
-Ralph
Ralph Neff   *   Packetvideo   *   www.pv.com
neff   pv.com   *  phone: 858-731-5408   *   fax: 858-731-5311